Why is "MODAL" not...

      % Make sure user doesn't have file locked/open in another process first...
      % Excel creates hidden file with "~$" prefix while open; search for this file
      chkOpen=true;
      while chkOpen
        [~,fn]=system(['dir /a:h /b ' fullfile(app.awardPath,['~$' app.awardFile])]);
        chkOpen=matches(strtrim(fn(3:end)),app.awardFile,'IgnoreCase',true);
        if chkOpen
          h=errordlg([app.awardFile "Locked for Edit.  Must Close Award File First."],'modal');
          waitfor(h)
        end
      end
      ...
      updateBillingSheet=false;
      [tBill,tPay]=readBilling(app.billQualFile,app.billSheet,updateBillingSheet);
      ...

Why without the waitfor(h) does the above code not wait for the user dialog but executes the call to readBilling immediately despite the 'modal' moniker on the error dialog?

The above fixes the problem, I'd just like to understand why "modal" isn't...

Answer 1

[Jan]

This is the documented behavior. See https://www.mathworks.com/help/matlab/ref/errordlg.html#mw_17038304-612a-4b3e-b4d7-2712205d1a0d :

"MATLAB program execution continues even when a modal Error dialog box is active. To block program execution until the user closes the dialog box, use the uiwait function."

This does not explain, why the dialog does not wait, but it clarifies that this is not a bug, but intented.